Anyway, I have a thread where users can post screenshots ... however, if the image is too wide, the right hand side will get cut off and the rest of it will not be viewable. Now I know there's an auto-resizer, however I'm hesitant to use that because people use different resolutions and it would severely distort some of the screenshots.

I visit another board that also uses forumotion, and they somehow have it so the full image is posted and the users are able to scroll over if they want to see the rest of the image.